This invention relates to shear machines and particularly to shear machines for use in the reprocessing of irradiated nuclear fuel elements.
After irradiation in a nuclear reactor irradiated nuclear fuel material may be processed to separate the fission products from re-usable nuclear fuel material. The separation of the re-usable nuclear fuel is usually a solvent extraction process and before such a process can be used the irradiated nuclear fuel material has to be dissolved in a suitable liquid medium which is usually nitric acid.
Nuclear fuel material for use in a nuclear reactor is contained in fuel pins. For ease of handling several fuel pins are combined together in a fuel element. The pins are held in a spaced apart relationship by grids and the fuel element has an outer tubular cover or wrapper. A method of separating the nuclear fuel material from the material which forms the fuel pins, grids and wrapper is required so that the amount of radioactive liquid to be treated in the reprocessing plant is as low as possible. One method of doing this is to preferentially dissolve the nuclear fuel material in the liquid medium leaving the material of the fuel pins, grids and wrapper to be disposed of as solid radioactive waste. Before the liquid medium can contact the nuclear fuel material the fuel pins have to be opened. This can be done by the use of a shear which shears the fuel pins into short lengths and thus allows the liquid medium to reach the fuel material.
Irradiated nuclear fuel elements are highly radioactive and the maintenance of a shear used to shear irradiated fuel has to be performed remotely. Maintenance is therefore difficult and time consuming resulting in long periods of time when the shear machine cannot be used.
Different reactor types use different types of fuel element and the requirements of a shear to shear each type of fuel element are also different. Therefore it is desirable to be able to change the shearing blade and the block on which the fuel element to be sheared is supported to suit each type of fuel element. Changing blades, like maintenance, is a difficult and time consuming operation because of the necessity to work remotely.